Controversy exists as to the role of age of asthma onset in childhood asthma. Data collected on self-reported physician-diagnosed asthmatics ages 6-24 yrs (N=376), who participated in the second National Health and Nutritional Examination, 1976-1980, a national cross-sectional sample, were examined to see if onset at or before age 2 years predicted future course. Early onset asthmatics tended to be more likely to have been ever hospitalized for a chest condition odds ratio (OR) = 2.3 (95% CI 0.7, 6.8), have chronic problems with phlegm (OR = 1.6 (95% CI 0.8, 3.4), be male OR = 1.7 (95% CI 1.0, 2.7). Late onset asthmatics tended to report more allergic rhinitis (OR = 1.5 (95% CI 0.8, 2.9), have at least one positiveprick-puncture allergen skin test (R = 1.5 (95% CI 0.7, 3.3), report excellent or very good health (R = 1.2, 3.7), be white OR = 2.2 (95% CI 1.1, 4.2), live in an urban area OR = 2 (95% CI 1.1, 3.7), have family incomes below poverty OR = 1.6 (95% CI 1.1, 2.5). No difference was found for reported chronic rhinitis, ever visiting an MD for chest condition, reporting asthma to be active, problems within the last 12 months with wheezing, cough attacks, or missing school. The sociodemographic and allergic characteristics varied by age of onset, but recent severity did not.